Place parsley, radishes greens, garlic, red wine vinegar, red pepper flakes, 3 Tbsp. oil and a good pinch of salt and pepper to taste in food processor or blender. Pulse 1-2 min until very smooth and incorporated.
Note: If no food processor or blender is available, simply mince parsley and garlic until very fine. Place in a small bowl with red wine vinegar, red pepper flakes, 3 Tbsp. oil and a pinch of salt and pepper and whisk well. Let sauce stand at room temperature until plating.